NEW YORK (Reuters Health) - The bright-light therapy often used to fight the "winter blues" may also ease major depression symptoms in older adults, a small clinical trial suggests.

Researchers found that of 89 older adults with clinical depression, those who were randomly assigned to three weeks of "bright light" therapy showed improvements comparable to what's been seen in studies of antidepressant drugs.

The therapy, which involves spending time with a "light box" each day, is a standard treatment for seasonal affective disorder, a form of depression that arises in the late fall and winter, when natural light is scarce.

But there's also evidence that light therapy can help some cases of non-seasonal depression.

Research suggests that bright light can affect levels of certain brain chemicals, like serotonin, thought to be involved in major depression. Light therapy also seems to zero in on the same brain structures that antidepressants target.

These latest findings, reported in the Archives of General Psychiatry, suggest that light therapy could offer an alternative to older adults with depression, who often cannot or do not want to take antidepressant drugs.

"I think bright light therapy definitely now deserves a place in the treatment of major depression in older adults," said lead researcher Dr. Ritsaert Lieverse, a psychiatrist at GGZ inGeest and the VU University Medical Center in Amsterdam.

"Many of them don't receive adequate antidepressant treatment because they refuse or resist (drug) treatment," Lieverse told Reuters Health in an e-mail. Older adults are also more vulnerable to drug side effects compared with younger people, he added.

That said, Lieverse stressed that people with depression symptoms should see a doctor rather than self-treat. Light boxes are available without a prescription -- online or at drug stores -- for a few hundred dollars, but that doesn't mean people should use them without medical guidance.

One reason, Lieverse said, is that major depression is a serious disorder that should be managed with the help of a professional.

Another is that light therapy is not for everyone. And older adults are more likely to have certain conditions that may preclude them from using light therapy -- including eye diseases like diabetic retinopathy.

The current study included 89 men and women age 60 or older who were randomly assigned to one of two groups. In one, participants were given a light-therapy box, donated by Philips Lighting, that emitted pale blue light; they were told to use it every morning for one hour over three weeks.

The rest of the study participants served as a "control" group. They were given boxes that emitted a dim red light, which has no known benefits or harms to the body.

After three weeks of treatment, the researchers found, the light-therapy group showed a greater improvement in scores on a standard measure of depression symptoms, the Hamilton Scale for Depression.

And three weeks after the therapy ended, more people in the light-therapy group were considered treatment "responders" -- meaning their depression scores had dropped by at least 50 percent. Of the light-therapy patients, 58 percent were responders, versus 34 percent of the control group.

Along with the changes in depression symptoms, the study also found some biological changes, Lieverse said.

Patients who underwent light therapy began to show a steeper rise in evening levels of the hormone melatonin, which promotes sleep. They also had a drop-off in levels of the "stress hormone" cortisol -- which, at the start of the study, had been elevated in the study group as a whole.

Lieverse said that the improvements in depression symptoms were on par with what has been seen with antidepressant treatment in older adults.

Light boxes typically range in price from about $100 to $500, and insurance may not cover the cost. They are generally considered safe, but can cause side effects like headache, eye strain, nausea and irritability.

There was some evidence that light therapy might also be helpful as an "add-on" treatment for older adults whose antidepressants are not working well enough.

One-third of patients in the light-therapy group were already on antidepressants -- but still depressed -- and had the light box added to their drug treatment. They were as likely to improve with light therapy as their counterparts who were not on medication.

Despite the positive findings, though, the study has limits. One is the small size, and another is the short-term follow-up. The researchers, who reported no financial ties to makers of the light boxes, say longer term studies are still needed to see how the benefits hold up over time.